1. Field of Invention
The invention relates to external surface additives for toners that have been treated with a fluorescent material. More in particular, the invention relates to a quality control method for identifying the presence and amount of an external surface additive of a toner through treatment of the target additive with a fluorescent dye.
2. Description of Related Art
Toners for use in modern xerographic printing machines are required to have specific properties, for example conductivity and triboelectric charging properties. The properties of a toner are set through the selection of materials and amounts of the materials of the toner. To ensure that the toner being produced will possess the requisite properties, it is thus necessary to carefully control the amounts of the materials used in making the toner.
Toners typically comprise at least a binder resin, a colorant and external surface additives. The external surface additives are generally added in small amounts. Examples of surface additives include, for example, silica, titanium dioxide, zinc stearate, etc. Prior to the present invention, various conventional analytical techniques were used to detect the presence and amounts of the various additives. For example, for detecting silica as an external additive, techniques such as X-ray Fluorescence and Inductively Coupled Plasma Spectroscopy have been used. Both of these methods utilize the characteristic light or x-ray energy emission of silicon (Si) at specific wavelengths to quantify the silica (SiO.sub.2). After measuring the silicon (Si) concentration, the silica (SiO.sub.2) level is then calculated. However, in a case where two different additives of the same type, for example two different silica additives, are present in the toner, these conventional techniques are unable to distinguish between the two additives.
What is desired, then, is an improved technique for determining the presence and amount of certain external surface additives in a toner.